It is oftentimes desirable to measure the displacement of a movable element relative to a related fixed element and to remotely indicate such displacement. Such can be the case, for example, where it is desirable to measure the displacement of a piston rod relative to the cylinder of a power actuator which can be utilized, again by way of example, on earth working implements such as plows or the like carried by a tractor carried by a road grader or the like.
Indicating devices have been heretofore suggested for indicating displacement of movable elements, including indicating displacement of a piston rod relative to the cylinder of a power actuator. Among such devices have been mechanical devices such as shown, by way of example, in U.S. Pat. Nos. 1,746,133; 3,077,179; 3,132,627; 3,275,174; 3,443,705; 2,704,047; 3,796,335; 3,883,021; and 3,900,073. In addition, stroke control of a piston is shown in U.S. Pat. No. 2,851,014.
Sensing of displacement of a movable element such as a piston has also been heretofore suggested in driven vehicles and such sensing has included, for example, the use of differential transformers or magnetic sensing (see, for example, U.S. Pat. Nos. 3,456,132; 3,956,973; 3,649,450; and 3,217,307).
In addition, sensing of movement of a movable element such as a piston, has also been sensed by mechanical means such as through the use of a ratchet and suitable other gearing (see, for example, U.S. Pat. Nos. 2,839,031 and 2,915,034) with the use of a ratchet and other gearing also having been heretofore suggested in conjunction with electrical circuitry for position indicating in U.S. Pat. Nos. 3,227,863 and 2,582,146, the latter of which also suggests the use of a variable resistance means in measuring water power.
Earth moving, or working, implements have heretofore been suggested having electro-mechanical indicating means for indicating the positioning of a blade or the like. Examples of such devices are shown in U.S. Pat. Nos. 3,512,589 and 2,972,194, the former of which includes switch controlled indicating lights and the latter of which includes a variable resistor the effective resistance of which is varied depending upon the blade cutting angle. In addition, earth working implements have also been heretofore suggested with indicating means that include a variable resistor the effective resistance of which is varied depending upon piston rod displacement of a power actuator (see, for example, U.S. Pat. No. 3,540,028).
Thus, while the prior art has suggested various types of electro-mechanical sensing devices including the use of variable resistors and associated circuitry for remotely indicating displacement of a piston rod relative to a cylinder of a power actuator, improvements in such electro-mechanical sensing devices are felt to be still possible.